Reducing Foam From Mixing Glyphosate Herbicides

Glyphosate formulations vary by product and year in regards to the amount of foam produced when preparing spray mixtures for weed control applications. Additional surfactants, water conditioners, and deposition management aids will help maximize glyphosate activity, but these also contain highly active surfactants that can cause excessive foam formation. Some adjuvants include a defoamer in their formulation to try to minimize foam, but even with this addition excessive foam can still result with certain products or tank mixtures.


  1. With the agitation off, begin filling spray tank with water.
  2. When the spray tank is approximately half full and while continuing to fill with water, add a water conditioning or AMS adjuvant in its entirety at the necessary volume.
  3. After the addition of water conditioner, add WCS Defoamer at 1–2 oz/100 gal to assist with preventing potential foam formation in the spray load. The required defoamer use rate will vary based on water source and glyphosate product used. Adding WCS Defoamer prior to adding the glyphosate product is important in the reduction of foam formation and will also lessen the need to “knock down” foam that has already formed, which tends to be more difficult and time consuming.
  4. After WCS Defoamer is added, add the glyphosate herbicide. Keep the agitation off.
  5. Once the sprayer is completely loaded with all products being used, turn on the agitation.
  6. Additional WCS Defoamer should not be necessary, but if foam does occur after agitation is started add additional WCS Defoamer as needed.


  1. Add wettable powders and dry flowables to the water prior to adding a water conditioner. Agitate until mixed, then turn off agitation. Only add water conditioners with agitation off.
  2. EC and Soluble Liquid Pesticides should also be added to the water prior to the water conditioner and with the agitation off.
  3. Add Micronutrient products either immediately before or after the glyphosate herbicide (but after the water conditioning agent).

d. Add drift control and/or deposition management products last (except for those possessing a water conditioner, which should follow the mixing procedure for water conditioners).